Automotive manufacturers in recent years have intensified research and development efforts to implement and commercialise more quickly vehicular fuel cell and gasoline hybrid electric vehicle (HEV) technologies. Fuel cell technologies utilize electro-chemical conversion devices, such as PEM and solid oxide fuel cells, to generate drive power with zero tailpipe emissions. Gasoline hybrids, while not completely eliminating tailpipe emissions, can significantly improve fuel economy at a fraction of the cost of present-day fuel cell technologies.
Alternatively, powertrains combining the benefits of hydrogen-powered internal combustion engines and hybrid electric functionality have been proposed. In U.S. Patent Application Publication 2002/0098414, for example, a very low emission hybrid electric vehicle is disclosed having a hydrogen-powered internal combustion engine, a metal hydride hydrogen storage unit, an electric motor and a nickel metal hydride battery. The problem however, due to the low power density of hydrogen gas when used in an internal combustion engine, is the ability of the powertrain to deliver gasoline engine-like performance over a wide range of operating speeds. This is so because hydrogen internal combustion engines are usually operated with a fuel-lean air/fuel ratio in order to preserve combustion stability.
As such, the inventors herein have recognized the need to adapt conventional internal combustion engine and HEV technologies to utilize hydrogen fuel and thus achieve substantial reductions in tailpipe emissions while maintaining hybrid functionality and performance comparable to conventional gasoline-powered engines.